1. Field of the Invention
The present disclosure relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device with good contrast ratio.
2. Discussion of the Related Art
A liquid crystal display (LCD) device is widely used in various fields of notebook computer, monitor, spacecraft, aircraft, and etc. owing to advantages of low driving voltage and power consumption and portability.
The LCD device includes a lower substrate, an upper substrate, and a liquid crystal layer between the lower and upper substrates. Liquid crystal molecules in the liquid crystal layer are aligned according to an application of electric field, whereby light transmittance is adjusted based on the alignment of liquid crystal molecules, to thereby display images.
Hereinafter, a related art LCD device will be described with reference to the accompanying drawings.
FIG. 1 is a cross section view illustrating a related art LCD device.
As shown in FIG. 1, the related art LCD device includes a lower substrate 10, an upper substrate 20, and a liquid crystal layer 30 between the lower and upper substrates 10 and 20.
On the lower substrate 10, there is an element layer 12 such as a thin film transistor. Also, a common electrode 14 and a pixel electrode 16 are alternately provided on the element layer 12, whereby an in-plane electric field is formed between the common and pixel electrodes 14 and 16.
On the upper substrate 20, there is a plurality of light-shielding layer 22. Also, a color filter layer 24 is formed between each of the light-shielding layer 22, and an overcoat layer 26 is formed on the color filter layer 24.
In order to improve a contrast ratio in the related art LCD device, the common electrode 14 and pixel electrode 16 are formed of an opaque metal material. The reason for using the opaque metal material is to improve the contrast ratio by good black luminance.
However, if the common electrode 14 and pixel electrode 16 are formed of the opaque metal material, externally-provided light may be reflected on the common electrode 14 and pixel electrode 16, whereby picture quality is deteriorated due to a rainbow-color image shown on a screen.